Mobile devices, such as but not limited to personal data appliances, cellular phones, radios, pagers, lap top computers, and the like are required to operate for relatively long periods before being recharged. These mobile devices usually include one or more processors as well as multiple memory modules and other peripheral devices.
Various timing constraints are imposed upon transistor based circuits. Some circuits should be faster then other circuits. Typically, the speed of a transistor-based circuit is responsive to various parameters including the voltage supplied to that circuit, the threshold voltage of the transistor, and the like.
In order to reduce the power consumption of a transistor based device lower voltage levels can be supplied to the device. These lower voltage levels can reduce the speed of the device and cause timing violations. U.S. Pat. No. 5,612,892 of Almulla, being incorporated herein by reference, describes one solution for reducing the power consumption of an integrated circuit.
In order to reduce the overall power consumption of a device one prior art solution involved providing high level voltage to a certain portion of the device while providing low level voltage to another portion of the device and providing level shifters between these portions. The first portion is also referred to as a critical path and usually includes logic paths such as portions of a processor. Each portion is also referred to as a frequency (or voltage) domain.
In many cases the number of level shifters is very large and the aggregate real estate required for the implementation of these level shifters is also large. Numerous level shifters require large area and consume a large amount of power.
Another power reduction technique involves voltage and/or frequency scaling and is known as DVS or DVFS. It includes altering the level of supply voltage as well as altering the frequency of the clock signal provided to a circuit, so as to adapt the power consumption of that circuit to an expected performance level of that circuit.
There is a need to provide a method and a system for providing voltage and clock signals to a system that includes multiple voltage supply units that may provide different supply voltages to different circuits.